1. Field of The Invention
The present invention relates to light source units and more particularly to a full-color flexible light source device comprising chip on board type red, green, and blue light source units (e.g., LEDs).
2. Description of Related Art
A conventional light source strip comprises a plurality of LEDs (light-emitting diodes) serially coupled together in which each LED has a coupled resistor and can emit light of single color. A number of drawbacks have been found when the above light source strip is modified to become a full-color light source strip. This is because brightness difference between any two of R (red), G (green), and B (blue) LEDs is quite large. For example, brightness of three R LEDs is equal to that of one B LED. Brightness of six G LEDs is equal to that of one B LED. For obtaining a uniform brightness of the light source strip, a unit thereof is required to consist of three R LEDs, six G LEDs, and one B LED. Such arrangement (i.e., optimum spacing) is difficult of achieving. It is often that an uneven illumination is occurred on the characters and/or marks of a billboard. This is not desirable. Moreover, the size of a full-color light source strip is about three times of that of a monochromatic light source strip if the former is adapted to emit light having a brightness the same as that of the latter. Also, the circuitry of the former is complicated, resulting in an increase in the manufacturing cost. Further, heat dissipation of LED is poor. As a result, LEDs tend to malfunction.
In U.S. Pat. No. 6,540,377 there is disclosed a full-color light source unit for solving the above problem. In the patent, the above unit consisting of three R LEDs, six G LEDs, and one B LED is modified to consist of only two R LEDs, two G LEDs, and one B LED. That is, the number of LEDs has decreased from ten to five. This is an improvement. However, the light source unit is rigid as illustrated in figures thereof. Moreover, the size thereof is quite large and spacing between any two LEDs is also relatively large. All of the above are not desirable. Thus, the need for improvement still exists.